This invention relates to an electronic digital calculator having a size and shape similar to a pen or pencil and containing a display screen, input value setting keys, and function keys which are arranged on the calculator so that it is easy to operate and almost free from an erroneous operation.
This kind of calculator heretofore used is set forth in U.S. Pat. No. 3,937,939 entitled "Single-Handed Digital Calculator." This conventional calculator is designed to be operated by one hand of the user so that a desired one of keys is actuated by the finger of the hand nearest it, with the body held by the thumb and the four other fingers of one hand of the user. If the number of keys to be selectively actuated is large, the keys are likely to be erroneously actuated, or the calculator itself becomes bulky, so that the abovesaid calculator is adapted to input two pieces of information by one key. Since the calculator is designed so that a plurality of pieces of information are selectively inputted by one key, the key actuation is not easy to perform and cannot be achieved rapidly. If the keys are actuated rapidly, an erroneous operation is likely to occur. Even if the keys of the abovesaid prior art calculator are selectively actuated by one hand of the user while held in the other hand, there is a fear of an erroneous key operation. In the case of using keys which are each capable of inputting only one piece of information as in an ordinary electronic digital calculator, even if the keys are reduced in size, the keys are inevitably disposed very close to adjacent ones of them when as many keys as 20 are mounted on the body of the same size as a pen. Consequently, when a desired one of the keys is actuated, the adjoining keys are liable to be pressed.
An object of this invention is to provide a pen type electronic digital calculator having a shape and size similar to a pen which is easy to operate and can be actuated rapidly and accurately.
Another object of this invention is to provide a pen type electronic digital calculator which employs keys, each inputting only one piece of information, and which can be operated rapidly and accurately.
Still another object of this invention is to provide a pen type electronic digital calculator designed so that keys do not hinder when the calculator is inserted into and taken out of a pocket.